Drill bit



7 June 28, 1938.

M. HOKANSON 2,121,914

DRILL BIT Filed Oct. 26, 1936 lull-:51?

INVENTOR.

ATTORNEY.

Patented June 28,1938

; tn u'rlau STATES PATENT OFFICE,

palm. BIT

Minnesota Application October 26,1036, Serial No. 107,583

Claims.

This invention relates to improvements in drill bits and pertains to that class of bit illustrated in my copending application Ser. No. 26,418.

The principalobiect of the present invention is 5 that of providing a more eilicient, faster cutting,

and durable bit of this type.

Another object is to provide such a bit having a cutting face in which a leading'portion thereof will effectually perform the work necessary with the least wear to that portion and assist materially in lessening the work necessary of accomplishment by the following portion.

Another object is to provide such a bit with.

novel and more efllcient fluid discharge therefore.

Still other objects and advantages of the invention will appearin the following description thereof.

Referring now to the accompanying drawing,

forming part of this application, and wherein like referencecharacters indicate like parts:

Figure 1 is a side elevation of one of the im-'..

proved bits.

Figure 21s a similar view taken at right angles to Figure 1. i a

Figure 3 is a plan view of the cutting face of the bit showing its relation to a hole formed thereby. Figure 4 is a section on the line H, Figure 3. In the drawing, i represents the body portion of the bit, the shank endthereof being hollow and internally screwthreaded as at 2 for the reception of any suitable extension necessary for such attachment. In this illustration of the embodiment of the invention I'have shown the sides of the'bit on one diameter as diverging, while upon the opposlte diameter they converge, thatis tosay, the periphery of the cutting face of the bit is of substantially elliptical form.

In the face of the bit are formed two concavities of cone shape,the apexes of which are illustrated at 3 and these concavities are so shaped and of such an extent as to cause their extreme circumferential edges to meet, or become tangent at the axis of the bit, as indicated at 4. As it is desired in this instance to make the central cutting portion of the face of the bit the leading portion, or that which operates upon a smaller diameter of the hole being drilled; the outermost slightly major portion of the edges of the concavitiesare cut away as at 5 and on a plane parallel with and spaced from that of the leading portion of the face of the bit along the axis thereof, thus forming a face stepped upon opposite sides as clearly illustrated in Figures 1 and 4 of the drawing, Thus it is apparent that the inner walls of length of the cutting edges 1 in the instant illustration being slightly greater than the length of the cutting edges 8. The outer inclined surfaces 8 of the stepped cutting edges I, as well as the outer inclined surfaces 9 of the inner cutting edges 6, are preferably of the same inclination as the innermost surfaces, though, obviously, and as various kinds of work might require, these inclinations may be varied. It is to be noted that as a preferred ratio of inner and outer'cutting edges, the termini of the former are defined by a circle intersecting or coincident with the axis of the cones which form the inner walls of same, resulting in the edges of the walls Iii of the ends of the centermost portion of the bit being arcuate in plan view (see Fig. 3) with the outer surfaces thereof being'parallel with the axis of the bit, though, obviously, such walls may be inclined, if preferred, as well as the inclination of both the inner and outer walls of the cutting edges to vary the reinforcement of same, as desired.

as previously stated, a novel feature of the inventlon is the arrangementof water discharge orifices and this is accomplished by there being formed in the bottom of the bore of the bit 2 an axial well ll into which the bore of the bit'rod,

not shown, discharges, and the supply of water through the axis of the bit being too common in the art to require further illustration. From this well axially is led a reduced bore l 2 to the tangential point of the cutting edges 6, previously described, and where said reduced bore may be countersunk as-desired for proper distribution of the water discharge therethrough. From opposite sides of the wellit are inclined holes I! leading to' the concavities of the 'cuttingedges andare novel in that they discharge within their re--- spective concavities to one side of the apexes thereof, or in other words forwardly of said apexes in respect to the travel of the bit. For example, in the illustration here shown and as viewedfrom the face of the bit (see Fig. 3), the travel of same during work is counterclockwise, so that the spalls from the bit are discharging rearwardly as quickly as possible and with the least eifort on the part of the liquid being used; where, of

course, if the bit traveled in the opposite direc- I tionthe discharge of the holes l3 would be on the opposite side of the apex of the cones from that illustrated. Thus formed, the discharge from the holes is readily led closer to the cutting edge of the bit and that without interfering with the.

strength of same, or the sharpening thereof.

From the above it is apparent that when this type of bit is used in connection with pneumatic jack hammers, drifting machines, stopers or the like, either as a part of the drill rod proper or a detachable bit, and in which cases the diameter of the hole drilledrarely exceeds 2%", the areas of the two spaced faces may be, for average drilling, substantially equal.

It will also be understood that this type of bit is adapted for use in large hole drilling, such as percussion'drilling in connection with oil wells, quarries, and the like.

In practice it has been found that the reaming function of this type of bit is very eflective as compared with that of the cross-bit, and that the loss in gauge of the bit is comparatively little, which, of course, is of extreme importance, because it will result in a greater diameter of hole at the conclusion of the drilling operation than that accomplished by the cross bit. The reason for this is the greater amount of wearing surface on the outside of the bit as compared with that of the cross-bit. Another advantage of this type of bit is that it does not rifle the hole like the common cross-bit, but leaves a smooth round wall which also prevents excessive circumferential wear of the bit.

The resharpening of this bit is also very easily performed. The dulled cutting edges of the bit are sharpened from the outside with the same angle as the original bit until it meets the circle of the cone. If a V-shaped grinding wheel is used for this, the same wheel can sharpen the cutting edges of the central cutting edges of the bit very nicely. If the cylinder of the central part of the cutting edges needs to be reconditioned, it can be done at the same timeas the taper of the bit is reconditioned.

Having thus described my invention, what I claim and desire to secure by Letters Patent, is:

1. A drill bit of the class described, characterized by the cutting face of said bit" being stepped, forming two separate parallel portions of said face, the inner inclined surface of ,he cutting edges ofsaid face upon either side of the axis of the bit being formed by the outer surfaceaxis of the bit being formed by the outer surface of a cone common to thecutting edges in both planes, and the outer inclined-surface of said cutting edges being formed as by the "inner surface of a cone concentric with said cone defining the inner inclined surface.

3. A drill bit of the character described, characterized by the cutting face of said bit being formed upon two parallel planes spaced apart longitudinally the axis of the bit, and conical depressions in said face, the edges oi. which form the cutting edges of the bit. in both planes.

4. A drill bit of the character described, characterized by the cutting face of said bit'being formed upon two parallel planes spaced apart longitudinally the axis of the bit, and conical depressions in said face, the edges of which form the cutting edges of the bit in both planes, that portion of said face adjacent the axis of the bit beingthe leading portion during the cutting action of the bit.

5. In a drill bit of the character described including a shank, a cutting face comprising two central arouately shaped cutting-edges diverging outwardly in opposite directions from the center ofthe bit, and two opposed arcuate cutting edges, one adjacent each of said central arcuate edges and of the same internal inclination as that of said arcuate cutting edges, each pair of said cutting edges being in a diflerent plane.

6. The combination with a drill bit having a concave cutting'face and an axial bore therein, of a discharge opening from said bore into the concavity of the face and located upon the following side of said concavity in respect to its rotation 'while drilling.

7. A hollow drill bit characterized by having a pair of arcuate cutting-edges meeting back to back adjacent the axial bore of said bit, and a substantially semi-circular cutting edge concentric with each of said arcuate edges, each pair of said edges being in a diiferent plane.

8. A drill bit of the character described, char acterized by the cutting edges of the bit being formed by conical depressions in said' bit and upon two parallel planes spaced apart longitudinally of andat right angles to the axis of the bit.

9. A unitary drill bit. of the character described, characterized by the cutting edges of the bit being formed upon separate parallel planes spaced apart longitudinally of the axis of the bit,

said cutting edges being formed by conical de' pressions extending in each plane.

10. A drill bit of the character described, characterized by the cutting edges of the bit being formed by conical depressions in said hit. an axial water bore through said bit, and a discharge opening from said bore into each conical depression and located upon the'foliowing side thereof in respect to the rotation of the bit while in the act of drilling.

1 noson. 

